Understanding the control of viral infections is of broad importance. Chronic HCV infection causes decreased expression of the iron hormone hepcidin, which is regulated by hepatic BMP/SMAD signaling. We found that HCV infection and the BMP/SMAD pathway are mutually antagonistic. HCV blunted induction of hepcidin expression by BMP6, likely via TNF-mediated downregulation of the BMP co-receptor HJV. In HCV-infected patients, disruption of the BMP6/hepcidin axis and genetic variation associated with the BMP/SMAD pathway predicted outcome of infection, suggesting BMP/SMAD activity influences antiviral immunity. Correspondingly, BMP6 regulated a gene repertoire reminiscent of Type I IFN signaling, including upregulating IRFs and downregulating an inhibitor of IFN signaling, USP18. Moreover, in BMP stimulated cells, SMAD1 occupied loci across the genome similar to those bound by IRF1 in IFN stimulated cells. Functionally, BMP6 enhanced the transcriptional and antiviral response to IFN, but BMP6 and related Activin proteins also potently blocked HCV replication independently of IFN. Furthermore, BMP6 and Activin A suppressed growth of HBV in cell culture, and Activin A inhibited ZIKV replication alone and in combination with IFN. The data establish an unappreciated important role for the BMPs and Activins in cellular antiviral immunity, which acts independently of, and modulates, IFN.

Hepcidin regulates systemic iron homeostasis. Suppression of hepcidin expression occurs physiologically in iron deficiency and increased erythropoiesis but is pathologic in thalassemia and hemochromatosis. Here we show that epigenetic events govern hepcidin expression. Erythropoiesis and iron deficiency suppress hepcidin via erythroferrone-dependent and -independent mechanisms, respectively, in vivo, but both involve reversible loss of H3K9ac and H3K4me3 at the hepcidin locus. In vitro, pan-histone deacetylase inhibition elevates hepcidin expression, and in vivo maintains H3K9ac at hepcidin-associated chromatin and abrogates hepcidin suppression by erythropoietin, iron deficiency, thalassemia, and hemochromatosis. Histone deacetylase 3 and its cofactor NCOR1 regulate hepcidin; histone deacetylase 3 binds chromatin at the hepcidin locus, and histone deacetylase 3 knockdown counteracts hepcidin suppression induced either by erythroferrone or by inhibiting bone morphogenetic protein signaling. In iron deficient mice, the histone deacetylase 3 inhibitor RGFP966 increases hepcidin, and RNA sequencing confirms hepcidin is one of the genes most differentially regulated by this drug in vivo. We conclude that suppression of hepcidin expression involves epigenetic regulation by histone deacetylase 3.

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First-line defence against viral infection is contingent upon rapid detection of conserved viral structural and genomic motifs by germline-encoded pattern recognition receptors, followed by activation of the type I IFN system and establishment of an intracellular antiviral state. Novel antiviral functions of bone morphogenetic protein and related activin cytokines, acting in conjunction with, and independently of, type I IFN, have recently been described. Activin A mediates multiple innate and adaptive immune functions, including antiviral effects. However, how such effects are mediated and how activin might be triggered by viral infection have not been defined. Here we addressed this in vivo and in vitro, in humans and mice. Transcriptomic analyses delineated strikingly congruent patterns of gene regulation in hepatocytes stimulated with recombinant activin A and IFNα in vitro. Activin A mRNA, encoded by INHBA, is induced upon activation of RIG-I, MDA5 and TLR7/8 viral nucleic acid sensors in vitro, across multiple cell lines and in human peripheral blood mononuclear cells. In vivo, infection of mice with influenza A also upregulated Inhba mRNA in the lung; this local upregulation of Inhba is retained in MAVS knockout mice, indicating a role for non-RIG-I-like receptors in its induction. Activin induction and signalling were also detectable in patients with chronic viral hepatitis. Together, these data suggest Activin A is triggered in parallel with type I IFN responses and can trigger related antiviral effector functions. This model has implications for the development of targeted antiviral therapies, in addition to revealing novel facets of activin biology.

Background The plasma cell malignancy multiple myeloma is usually incurable, partly because the bone marrow niche provides a protective microenvironment for quiescent tumour cells. We hypothesised that bone morphogenetic protein (BMP) signalling, a crucial regulator of cell diff erentiation in bone marrow, would be altered by multiple myeloma and that pharmacological interventions that manipulate BMP activity have potential to alter disease progression. MethodsIn vitro, we used human and mouse cell lines and mouse primary stromal cells to test the interaction of BMP signalling with niche and tumour components. In vivo, we used the C57BL/KaLwRij mouse myeloma model to test the eff ect of BMP signalling disruption with a small molecule LDN-193189 (LDN) on disease progression (as measured by paraprotein and tumour cell number), bone lysis (micro-CT imaging of femoral metaphysis), and anaemia (haemoglobin and production of hepcidin). FindingsTumour BMP signalling activity was increased 10 fold when myeloma cells were cultured with bone marrow stromal cells, but this eff ect was abrogated by BMP signalling inhibitor LDN. Expression of RANKL, a major mediator of myeloma-induced bone lysis, was reduced 1•6 fold by LDN in stromal cells from myeloma-bearing mice (p=0•03). Consistent with this, in vivo, LDN improved bone volume signifi cantly in myeloma-bearing mice (total femoral bone to tissue volume ratio 36•2 vehicle group, 38•8 LDN group, n=10; p=0•015). LDN also altered the niche-preference (endosteal vs central marrow) of tumour cells to favour the endosteal niche, reported to house the quiescent stem fraction of a multiple myeloma clone (ratio of endosteal to central marrow myeloma cells 0•23 vehicle group, 0•37 LDN group, n=8; p=0•034). Serum hepcidin correlated with disease burden (r²=0•55 p=0•03), which was partly reversed by LDN.Interpretation Our fi ndings show that BMP inhibition improves bone disease in multiple myeloma, possibly by reducing RANKL levels. RANKL inhibitors are eff ective in multiple myeloma bone disease, so there is potential for therapeutic benefi t to BMP inhibition in this context. The additional benefi t of hepcidin reduction could alleviate infl ammatory anaemia associated with multiple myeloma. However, the LDN-induced alteration of niche preferences by tumour cells might imply changes to stem-cell quiescence, which is now being investigated.

Background: First-line defence against viral infection is contingent upon rapid detection of conserved viral structural and genomic motifs by pattern recognition receptors, followed by activation of the type I IFN  response and establishment of an antiviral state. Novel antiviral functions of bone morphogenetic protein and related activin cytokines, acting in conjunction with, and independently of, type I IFN, have recently been described. How these antiviral effects are mediated and triggered by viral infection has not been defined. Methods: Microarray and RNAseq data from hepatoma-derived cell lines stimulated with Activin A in vitro were interrogated both by pathway analysis and for evidence of IFN-stimulated gene induction. Liver tissue obtained from patients with chronic HCV were examined by real-time quantitative polymerase chain reaction (RT-qPCR) for evidence of Activin A induction. Activin expression by peripheral blood mononuclear cells exposed to nucleic acid analogues was quantified by RT-qCR, whereas induction dynamics in acute infection was investigated in in vitro Sendai virus infection and a murine influenza A. Results: Transcriptomic analyses delineated strikingly congruent patterns of gene regulation in hepatocytes stimulated with recombinant Activin A and IFNα in vitro. Activin A mRNA, encoded by INHBA, is induced upon activation of RIG-I, MDA5 and TLR7/8 viral nucleic acid sensors in vitro, across multiple cell lines and in human peripheral blood mononuclear cells. In vivo, imurine influenza A also upregulated Inhba mRNA in the lung; this local upregulation of Inhba is retained in MAVS knockout mice, indicating roles for non-RIG-I-like receptors in its induction. Activin induction and signalling were also detectable in patients with chronic viral hepatitis. Conclusions: These data suggest Activin A is triggered in parallel with type I IFN responses and can trigger related antiviral effector functions, with implications for the development of targeted antiviral therapies and revealing novel facets of Activin biology.

A combination of sub-therapeutic chelation and subsequent iron overload are regarded as the principal drivers of endocrine dysfunction in thalassaemia. The clinical presentation of endocrine complications and their timing of onset can be highly variable, in part due to population heterogeneity but also variation in chelation strategies. Endocrinopathies commonly associated with thalassaemia include: growth delay; pubertal delay; gonadal dysfunction; thyroid disorders; parathyroid and adrenal gland impairment; impaired bone metabolism; and type 2 diabetes mellitus. In this chapter we summarise the main presentations of endocrine disorder in thalassaemia, summarising their epidemiology, clinical presentation and pathophysiologic basis. Furthermore, we review screening, monitoring and treatment strategies, with particular regard to the UK Thalassaemia Society’s 2016 National Standards.

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